The ability to promote tissue regrowth in vivo can facilitate wound healing and post-surgical recovery of patients who have suffered tissue damage or destruction. A variety of methods and compositions have been used to repair or regenerate bone tissue in vivo. The need for such methods and compositions is readily apparent, when considering that in 1999, approximately 500,000 bone graft procedures were performed in the United States alone. Ideal bone graft materials for use in such procedures possess characteristics necessary to induce new bone growth, namely osteoconductivity and osteoinductivity.
Osteoconductivity refers to a graft's ability to support the attachment of new osteoblasts and osteoprogenitor cells. The osteoconductive components of a graft provide an interconnected structure through which new cells can migrate and new blood vessels can form. Osteoinductivity refers to the ability of a graft to induce nondifferentiated stem cells or osteoprogenitor cells to differentiate into osteoblasts.
In 1998, nine out of ten bone graft procedures performed in the United States involved the use of either autograft or allograft bone tissue. Despite the benefits of autografts and allografts, the limitations of each have necessitated the pursuit of alternative graft materials. Using basic criteria necessary to a successful graft (e.g., osteoconduction and osteoinduction), investigators have developed several bone graft substitutes. These can contain a variety of materials, including natural and synthetic polymers, ceramics, and composites; and in some instances, production of bone graft substitutes can involve biotechnological strategies (i.e., factor- and/or cell-based strategies). Non-demineralized bone, such as freeze-dried cortical particulate, is the most often used osteoconductive bone grafting material.
Osteoinductive substances found in some bone graft substitutes are demineralized bone particles and/or powder. Contained in the extracellular matrix of bone tissue is a full cocktail of bone growth factors, proteins, and other bioactive materials necessary for osteoinduction and, ultimately, successful bone healing. To capitalize on this cocktail of proteins, bone tissue can be demineralized, leaving the osteoinductive agents in the demineralized bone matrix (DBM). Such osteoinductive DBM can be incorporated into a number of different bone graft substitutes.
While a number of different materials thought to enhance osteoconductivity (i.e., purified or partially purified polymers) have been used in bone graft substitutes, new, more easily prepared, osteoconductive/structural materials for combining with demineralized or non-demineralized bone to produce a bone graft substitute are desirable.